Synthesis of Substituted N'‐(3,5,6,7,8‐Pentafluoro‐1,4‐Dioxo‐1,4‐Dihydronaphthalen‐2‐yl)Hydrazides by Condensation of Acyl Hydrazines and Perfluoro‐1,4‐Naphthoquinone

Abstract

The reaction of different acyl hydrazines with hexafluoro‐1,4‐napthoquinone was studied for the first time. It was demonstrated that this interaction stops at the substitution of one fluorine atom in the quinone moiety. Based on the observed reaction, a general approach to the synthesis of different pentafluoro‐1,4‐dioxo‐1,4‐dihydronaphthalen‐2‐yl hydrazides was developed. It was revealed that optimal conditions for the condensation of hexafluoro‐1,4‐napthoquinone with hydrazides are reflux in MeOH for 0.25 h; note, the protocol does not require any chromatographic purification of the target products. The method is versatile and makes it possible to prepare products containing various substituents in the aryl part of the molecule. In addition, alkyl and heteroaryl hydrazides can be employed as starting compounds too, and the presence of hydroxy and cyano groups in the applied acyl hydrazines does not interfere with the condensation. The structure of one of the obtained products, namely 4‐chloro‐N□‐(3,5,6,7,8‐pentafluoro‐1,4‐dioxo‐1,4‐dihydronaphthalen‐2‐yl)benzohydrazide, was confirmed by X‐ray diffraction. In crystals of this hydrazide, both NH groups form intermolecular hydrogen bonds that give rise to layers lying in the [001] plane. Prepared N'‐(3,5,6,7,8‐pentafluoro‐1,4‐dioxo‐1,4‐dihydronaphthalen‐2‐yl)hydrazides are of interest as redox‐active ligands and precursors for obtaining a wide range of functionalized 1,4‐napthoquinones for medicine chemistry.